Companion to the wet-bulb thermometer in a psychrometer. Used to measure ambient air temperature.

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

In general. the severe wind of an intense tropical cyclone (hurricane or typhoon). The term has no further technical connotation, but, unfortunately, is easily conftlsed with the strictly defined hurricane-force wind,

The total of direct solar radiation and diffuse sky radiation received by a unit horizontal surface. Global radiation is measured by pyranometers.

A sudden brief increase in the speed of the wind, followed by a lull or slackening. Compare to peak gust.

By international agreement, a period during which greatly increased observation of world-wide geophysical phenomena is undertaken through the co-operative effort of participating nations. July 1957-December 1958 was the first such year. However, precedent ...

See mote.

A method of winds aloft observation accomplished by tracking a balloon-borne radar target or radiosonde with either radar or a radio theodolite.

A pressure tube anemometer, consisting of a pitot tube mounted on the windward end of a wind vane and a suitable manometer to measure the developed pressure and calibrated in units of wind.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

Same as evaporative power.

Radio Direction Finder.

The boundary between the troposphere and stratosphere, usually characterized by an abrupt change in lapse rate. Its height varies from 10 to 20 km. Regions above the tropopause have greater atmospheric stability than regions below.

The condition of the atmosphere when the amount of water vapor present is the maximum possible at the existing temperature.

Dihydrogen oxide, molecular formula H2O.

A systematic summary of the terms (inflow, outflow, and storage) of the storage equation as applied to the computation of soil-moisture changes, ground-water changes, etc. An evaluation of the hydrologic balance of an area. Also called basin accounting, w ...

A balloon having a detachable tail which is released when the balloon has undergone a predetermined expansion. It thus serves to measure approximately the density of the atmosphere at the point of release.

A colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

A navigational aid used to facilitate the landing of an aircraft at an airport in instrument weather, i.e. low visibility.

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.